1. Field of the Invention
The invention relates to a semiconductor switch and limiter device and, in particular, to a GaAs current limiter and switch having a control groove preferably formed with a focused ion beam.
2. Description of the Prior Art
In many high frequency and radio frequency (rf) applications, and in particular, those of microwave frequency, it is often necessary to design circuit systems which have a high degree of signal and power isolation between certain parts thereof. For example, an ordinary radar system must have the capability of both transmitting and receiving microwave signals. The designer is faced with the problem of electrically isolating the transmitter and receiver functions of the system due to the different operating characteristics of each. Typically, a radar transmitter will operate at power levels near 1 kilowatt whereas a radar receiver will quickly saturate at power levels of about one milliwatt. In order to prevent the electrical coupling of transmitter power to the receiver, a switch device is typically designed into the antenna between the transmitter and receiver circuits to prevent the transmission of power thereinbetween.
Switch devices have long been available in the prior art. For example, silicon PIN diodes have been utilized in the microwave application described hereinabove. However, PIN diode switches have high power dissipation when biased in the forward or "on" state and require a large reverse bias (typically 10-30 volts) to drive the switch to the "off" state and prevent current flow. Thus the design of the driver/power supply required to switch the PIN diode between "on" and "off" states is often very complex. Finally, PIN diodes generally have a slow response time. These disadvantages in the use of PIN diodes have caused system designers to look for alternatives.
The design of modern high speed integrated circuits has advanced to the point where many circuit components and functional blocks are provided on extremely small chip areas. Commonly, it has become necessary for designers to minimize the power dissipation of each circuit element formed on the chip. Thus, in those circuit applications wherein a high speed switch is required and wherein monolithic techniques are practical, the PIN diode switches described hereinabove would not be practical due to their relatively large power dissipation.
The cost effectiveness of a microwave circuit would be enhanced if the circuit had the capability of performing more than one function. For example, it would be desirable if the electrical isolating device described above functions as a power limiter, in addition to its switching function, particularly in limiting the amount of power that could be passed, or transmitted as in the radar application described above. Existing PIN diodes cannot function as a passive limiter.